BATTERY SYSTEM COMPRISING A MEANS FOR MEASURING AN INTERNAL PRESSURE TO CONTROL A RECHARGING INSTRUCTION

Abstract

The present invention relates to a battery system (1) comprising elements (9) for storing electrical energy, a control means (2) capable of calculating a recharge instruction (CRL) and a means (5) for clamping the elements (9), further comprising a means (4) for measuring a parameter representative of a measured pressure which is exerted by the elements (9) on the surface of said clamping means (5) and in which the control means (2) delivers a limited recharge instruction (CRL) as a function of said parameter. The invention also relates to a method for controlling the recharge controlling a recharge instruction as a function of said parameter representative of the measured pressure. The invention applies for example to electrified vehicles comprising a traction battery. Figure 1

Description

Title of the invention: BATTERY SYSTEM COMPRISING A MEANS FOR MEASURING AN INTERNAL PRESSURE TO CONTROL A RECHARGING INSTRUCTION

[0001] The field of the invention relates to a battery system and a method for controlling the recharging of said system. The invention applies in particular to an electrified vehicle and aims to optimize the lifespan of a battery.

[0002] Electrified vehicles are equipped with a high-power traction battery generally comprising several electrochemical cells, for example of the Lithium-ion type. For this type of technology, a cell comprises a wall and internal elements comprising a positive electrode, a separator and a negative electrode. For the proper functioning of a cell, these elements must be kept in contact in a positive force range. In operation, chemical reactions generate gases and an expansion of the electrodes, then producing a pressure pushing the walls.

[0003] This pressure increases as a cell ages. This is the pressure resulting from the increase in the passivation layer proportionally to the aging state. Furthermore, it has been observed that the pressure fluctuates significantly during variations in the state of charge level during charging and discharging. This results in a force resulting from the expansion of active materials proportionally to the instantaneous state of charge level. This latter phenomenon is called respiration or "Breathing" according to the English term.

[0004] The increase in pressure resulting from both aging and respiration of the cell tends to decrease the pressure between electrodes and separators. To prevent their separation, it is common to enclose a cell or a set of cells in a rigid frame to keep the internal elements in contact.

[0005] As a cell is used, the increase in internal pressure affects the aging of the cell and therefore determines the end of life. For electromobility applications, the end of life is generally set at a loss of energy storage capacity of approximately 20%. In view of the mechanical deformations observed between cells and the ends of the rigid frame, values ​​of the order of 25 kN of tensile force on the sides of the frame have been measured for an aging state of 20% and values ​​of 5 kN for a new state.

[0006] Battery system frames are sized for a maximum pressure level and for a given aging state, linked to an acceptable loss of energy capacity for the intended application. When the force applied to the surface of the cells by the internal elements reaches the intended limit, the use of the battery is stopped to avoid the risk of fire due to rupture of the cells or a module.

[0007] For this purpose, car manufacturers are developing algorithms for estimating the aging state of batteries to define the end-of-life period. A known method consists of counting the number of charge and discharge cycles and deciding to replace the battery when a limit is reached. However, the constraint assumptions used are not always realistic because the level of aging depends mainly on the actual use of the battery. In some cases, the use of the battery could be extended without risk of malfunction.

[0008] Furthermore, the lifespan of battery systems could be increased in return for larger, heavier batteries and a reinforced frame as well as a greater reduction in total capacity. However, these solutions are not recommended in the field of electromobility.

[0009] It is also known to implement methods for controlling temperature and limiting the charging current, in particular for fast charging. For example, document FR2952235A1 is known describing a recharging method in which the voltage measured at the terminals of the battery is compared with a voltage threshold in order to control the end of charging and in which the threshold is provided by a table which is a function of the measured temperature and the current flowing in the battery. The use of this table aims to avoid physical damage to the battery and improve its longevity. Other strategies recommended by certain manufacturers aim to reduce the target state of charge level at the end of recharging, set for example to 80% of the maximum total available capacity, to reduce the stress on the cells caused by a high state of charge.

[0010] The invention aims to overcome the aforementioned problems. One objective of the invention is to extend the life of a battery. Another objective is to adapt the management of the recharging of a battery according to the aging of the electrochemical cells. Another objective is to improve the estimation of the level of aging of a battery and adapt the energy management in accordance with its use.

[0011] More specifically, the invention relates to a battery system comprising electrical energy storage elements, a control means capable of calculating a recharging instruction and a means for clamping the elements. According to the invention, the system further comprises a means for measuring a parameter representative of a measured pressure which is exerted by the elements on the surface of said clamping means and the control means delivers a limited recharging instruction as a function of said parameter.

[0012] According to a variant, the measuring means comprises at least one strain gauge delivering a measurement of the elongation of the gripping means.

[0013] According to a variant, the measuring means comprises at least one strain gauge delivering a measurement of the elongation of the battery or a measurement of the elongation of the wall of an electrical energy storage element.

[0014] According to a variant, the measuring means comprises at least one pressure sensor fixed between the energy storage elements and the clamping means.

[0015] According to a variant of the system in which the energy storage elements are electrochemical cells, the measuring means comprises at least one pressure sensor fixed between two electrochemical cells on the surface of one of said two cells.

[0016] According to a variant, the means for enclosing is a rigid frame made of metallic material.

[0017] According to the invention, there is provided an electrified vehicle comprising a battery system according to any one of the preceding embodiments.

[0018] According to the invention, a recharge control method is provided for such a battery system comprising the following steps:

[0019] - The determination of a parameter representative of a measured pressure which is exerted by the electrical energy storage elements on the surface of said means for enclosing,

[0020] - The control of a first limited recharging instruction as a function of said setting.

[0021] According to a variant, the control of the first limited recharge instruction consists of determining a recharge limitation coefficient as a function of the parameter relative to a recharge limitation threshold, the value of the first limited recharge instruction being a function of a second recharge instruction multiplied by the limitation coefficient.

[0022] According to a variant, when the value of the parameter is greater than or equal to the limitation threshold, the limitation coefficient is equal to a first value controlling the stopping of the recharging of the battery system.

[0023] According to a variant, when the value of the parameter is lower than the limitation threshold, the limitation coefficient is equal to a second value which is a function of a difference between the value of the parameter and the limitation threshold.

[0024] According to a variant, the first recharging instruction is a maximum authorized charging current instruction, the first value of the coefficient is equal to 0, and the second value is a value strictly greater than 0, between 0 and 1, for example 0.5, 0.75, 0.90 or 1.

[0025] According to a variant, the first recharging instruction is a state of charge level maximum allowed, when the parameter value is greater than or equal to the limitation threshold, the maximum allowed state of charge level is strictly lower than the available charge level, for example is equal to 90% of the maximum available charge level, or 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the maximum available charge level.

[0026] The invention improves the management of electrical recharging in that it is controlled in a manner adapted to the aging of the battery by monitoring the internal pressure of the electrochemical cells. Thanks to the invention, it is possible to extend the life of a battery, by accepting a limited maximum state of charge level and controlled specifically according to the method. The invention makes it possible to monitor the increase in internal pressure of the cells and to control the stopping of recharging in the event of a risk of cell rupture.

[0027] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0028] [Fig-1] schematically represents a battery system according to the invention.

[0029] [Fig.2] represents a functional diagram describing the means of controlling the recharge provided to control the recharge control method according to the invention.

[0030] [Fig.3] is a graph schematically illustrating the evolution of the level of aging of a battery and control of recharging according to the invention as a function of the pressure exerted by the electrical energy storage elements of the battery.

[0031] [Fig.4a] schematically represents an alternative embodiment of the system of battery with a pressure sensor.

[0032] [Fig.4b] schematically represents another variant embodiment of the system of battery with a pressure sensor.

[0033] The invention applies to the field of electrochemical batteries, in particular in the field of electrified vehicles, but not exclusively. The battery system and the associated method find an application in the field of charging control management applications in stationary applications, electromobility and any electronic device with a battery system. By way of non-limiting example, the preferred embodiment of the invention will be described for an electrified motor vehicle application comprising a high-power traction battery. In the present description, the term approximately means + / -10% of the indicated value and the limits of a range of values ​​are included in the range.

[0034] The invention aims to stop recharging and / or gradually reduce recharging as a function of a parameter representative of an internal pressure of the battery. The invention has the effect of gradually reducing the state of charge level maximum allowed depending on battery aging.

[0035] In [Fig. 1], a preferred embodiment of the battery system according to the invention for an electrified vehicle has been schematically described. The battery system 1 comprises a module 3 comprising electrical energy storage elements 9 comprising a plurality of electrochemical cells, in this non-limiting example of Lithium-ion type technology. An electrochemical cell comprises a wall and internal elements comprising a positive electrode, a separator and a negative electrode. The internal elements of a cell must be kept in contact in a positive force range. The wall of a cell may be cylindrical, prismatic or in the form of a film (so-called “Pouch Cell” technology). The battery system 1 further comprises a means 2 for controlling the recharge.The control means 2 is provided to at least develop a recharging instruction for the energy storage elements 9 in accordance with the method according to the invention.

[0036] The battery system 1 is electrically rechargeable by means of electrical lines 8 connected to a charging control device 6 of the electrified vehicle. The charging control device 6 is electrically connected to an electrical charging source 7. The electrical source 7 may be an electricity generating machine, for example the electric traction machine of the vehicle, or a charging terminal external to the vehicle. For example, the charging control device 6 comprises charging means cooperating with an electrical outlet so as to be able to electrically connect to the external charging terminal 7 connected to an electrical supply network, generally operating at alternating voltage. The terminal 7 may deliver a direct or alternating current.High voltage contactors are generally provided which ensure the disconnection / connection of the battery 1 with the vehicle's power electrical circuit, the charging control device 6 and the electrical outlet.

[0037] The battery system 1 further comprises a means 5 for enclosing the electrochemical cells 9. In this embodiment, the means 5 for enclosing is a rigid metal frame external to the electrochemical cells, made of an aluminum-type material for example. The rigid frame 5 encircles or surrounds a group of several electrochemical cells 9 as can be seen in [Fig.l] so as to exert a positive pressure against the surface of the walls of the cells 9. The frame 5 is arranged to apply pressure to only a portion of the wall of the cells, for example on each side of the cells laterally. It is not excluded that the frame 5 can completely frame or enclose the electrochemical cells, for example in the form of a box. The pressure exerted by the frame 5 is then applied in the latter case to the lateral faces and the upper and lower faces of a cell.

[0038] Frame 5 is commonly referred to by the English terms “casing”, “side plate" or "end plate", or the terms strapping, casing, belt. It frames the module 3 of a group of cells 9. In another embodiment, it is envisaged that each cell of a battery can be enclosed by a frame 5. In another embodiment, the enclosing means 5 forms the external wall of an electrochemical cell. The pressure applied by the enclosing means 5 is intended to keep the electrodes in contact against the separator inside each cell.

[0039] In the case of a non-limiting example, of a prismatic cell with dimensions 28mmx7mmxl4mm, at the start of life, the force applied by the frame 5 to the surface of a cell is 5k.N. For an aging state at the end of life specified for example for a motor vehicle, the force applied by the frame 5 varies between 20k.N and 25k.N, with fluctuations of the order of 5k.N resulting from the respiration of the cells.

[0040] The state of aging can be designated by the acronym SOHc for “State of Health on capacity” and corresponds to the aging level parameter of the battery expressed by a ratio between the maximum quantity of electricity storable at a given time and the maximum quantity of electricity storable in the new state of the battery.

[0041] The state of charge level can be designated by the acronym SOC for “State of Charge” and corresponds to the state of charge level of the battery expressed by a ratio between the quantity of energy stored at a given instant and the maximum quantity of energy storable at a given instant. The parameters SOHc and SOC are expressed in percents.

[0042] The applied forces which could be measured during the life of a cell or during testing make it possible to establish a recharge limitation threshold aimed at stopping an expansion of an electrochemical cell resulting from an increase in the state of charge.

[0043] The battery system 1 further comprises a pressure measuring means 4. The measuring means 4 has the function of measuring a parameter representative of a pressure which is exerted by the electrical energy storage elements 9 of the battery 1 on the surface of the frame 5. In this preferred embodiment of the invention, the measuring means 4 is a strain gauge arranged to measure an elongation of the rigid frame 5 or the elongation of an electrochemical cell 9 of the battery 1. The strain gauge is fixed on the surface of the frame 5 or on the surface of the wall of a cell. The strain gauge 4 delivers a voltage signal to the control means 2, the value of which is proportional to the elongation of the frame 5.

[0044] Any other measuring means is conceivable without departing from the scope of the invention. The measuring means may be a pressure sensor or a piezoelectric technology sensor for example. Such a sensor is fixed between an electrochemical cell 9 and the frame 5, or alternatively between two electrochemical cells 9.

[0045] Monitoring this parameter allows the control means 2 to develop a CRL recharging instruction according to the invention, for example an end of recharging command. recharge when this parameter exceeds a chosen threshold. Additionally or as an alternative variant, the control means 2 is configured to develop a command to reduce the charging current gradually according to said parameter.

[0046] The control means 2 is intended for the supervision of the battery system 1. It is capable of delivering to other computers of the vehicle information on the state of the battery, such as a value representative of the SOC, the SOHc, the temperature, the charging current flowing through the battery or the no-load voltage in particular, as well as instructions intended for the charging control device 6 and / or a charging terminal 7, in particular an authorized charging power, a charging mode, a maximum charging current, or a current limitation instruction. A communication bus is provided, for example of the CAN (Controller Area Network) type, allowing the control means 2 to communicate the charging instructions to other computers.

[0047] The function of the charging control device 6 is to manage the communication between the different charging stations and to monitor and control the electrical charging at the station. The charging device 6 also comprises an electrical converter of the alternating / direct AC / DC and direct / direct DC / DC type. In charging situations at the station, it converts an alternating voltage to a direct AC / DC voltage, in particular during charging in mode 2 or mode 3 in which it is necessary to convert an alternating voltage in 220V (of the single-phase or three-phase type) to a direct voltage compatible with the battery system, up to 450V or 1000V for example in this embodiment. In a driving situation, another function is the DC / DC conversion between the battery and the on-board systems of the vehicle, for example the on-board network in 14V, the low-voltage battery and the electric traction machine of the powertrain.

[0048] In the context of so-called fast or mode 4 recharges, the recharge voltage is delivered directly by terminal 7, that is to say without modification of the voltage by the voltage converter. The voltage delivered by terminal 7 is of the direct type, generally greater than 300V, in this example between 400V and 500V, and is directly applied to the terminals of the battery 1 through the high-voltage contactors. For this type of charge, the recharge device 6 delivers to terminal 7 the recharge instruction CRL calculated by the control means 2 of the battery system 1.

[0049] The control means 2 is provided with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute a method for controlling the recharge according to the invention. But this is not obligatory. Indeed, the computer could be external to the control means 2, while being coupled to the latter. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. By Consequently, the control means 2, according to the invention, can be produced in the form of software modules (or computer modules (or even “software”)), or electronic circuits (or “hardware”), or even a combination of electronic circuits and software modules.

[0050] In [Fig.2], the functional module of the control means 2 of the battery system 1 provided to enable implementation of the recharge control method according to the invention has been described. In this embodiment, it conventionally comprises a first module 20 configured to calculate a recharge setpoint CR.

[0051] In this preferred embodiment, the recharging setpoint is a maximum authorized recharging current setpoint. The CR current setpoint is determined as a function of the current state of charge SOC, the aging state SOH, and the temperature in particular. The CR current setpoint is delivered for example by a predetermined map, established in design and recorded in the memory of the control unit 2 of the battery system 1, taking as input the current state of charge SOC and the temperature of the battery 1.

[0052] More precisely, the control means 2 receives as input a measured value of the temperature of the battery from one or more temperature sensors, as well as a measured value of the total voltage of the battery 1. In a manner known per se, the total voltage of the battery 1 can be determined from information measured at the electrochemical cells 9. The current flowing through the battery is determined from current sensors of the battery 1. In addition, the control means 2 is able to determine the state of charge level SOC of the battery 1 at any time, for example expressed as a % of the total capacity of the battery, from equivalence tables with the measured voltage and a state of health or aging state indicator SOH. The table or tables are recorded in the memory of the control means 2 and can be consulted at any time by its computer.

[0053] The recharge control method according to the invention comprises a step of determining a parameter P representative of a measured pressure which is exerted by the internal elements of the battery on the surface of said clamping means and a step of controlling the limited recharge instruction CRL as a function of said parameter P. The recharge instruction CRL is a maximum accepted current instruction.

[0054] More precisely, to determine the recharge setpoint CRL, dependent on the internal pressure of the battery in accordance with the invention, the strain gauge 4 delivers an elongation value M of the frame 5 to the computer 2. The value M is proportional to the elongation of the frame 5. The value M is multiplied, illustrated by the multiplier block in [Fig.2], by a stiffness coefficient K, proportional between the elongation and the force exerted by the internal elements of the battery 1. K is a coefficient predetermined in design and recorded in memory. The control means 2 therefore continuously calculates during use of battery 1 the value of parameter P, where P = K*M. P is a parameter whose value is representative of the force exerted by the internal elements of battery 1 on frame 5.

[0055] In this preferred embodiment of the method, the control of the limited recharge instruction CRL consists of determining a coefficient of limitation CL of the recharge as a function of the parameter P in relation to a threshold of limitation of the recharge SL.

[0056] For this purpose, the control means 2 comprises a second module 21 whose function is to calculate the limitation coefficient CL. The function of the limitation coefficient CL is to limit the recharging setpoint CR and / or to gradually reduce the value of the recharging setpoint CL, until the end of recharging when the pressure is greater than a predetermined limitation threshold.

[0057] In this embodiment, the limitation coefficient CL is multiplied by the value of the current setpoint CR to calculate the limited recharge setpoint CRL, illustrated by the multiplier block in [Fig.2]. The limitation coefficient CL takes values ​​in a range delimited by the values ​​0 and 1, in a binary or gradual manner.

[0058] In an embodiment in binary limitation control or of the “all or nothing” type, the coefficient CL is equal to 1 as long as the value of the parameter P is lower than the pressure limitation threshold SL. The limitation coefficient CL is equal to zero when the value of the parameter P is greater than or equal to the threshold SL. The value 0 therefore controls the stopping of the recharge because the maximum authorized current setpoint is equal to 0 amperes. The threshold SL is calibrated for example to a value of approximately 25kN. The value of the threshold SL depends on the dimensions and characteristics of the frame 5 and the constraint criteria specific to the battery system 1. This value is in no way limiting of the invention.

[0059] In an embodiment in gradual limitation control, the coefficient CL is equal to a value between 0 and 1 depending on the difference between the value of the parameter P and the value of the threshold SL. The value is equal to 1 when the difference is greater than 2kN, i.e. for a pressure P up to 23kN. The value of CL is equal to 0.5 for a pressure P equal to 24kN and the value of CL is equal to 0 when P is equal to or greater than 25kN. Other coefficient values ​​are conceivable without departing from the scope of the invention.

[0060] The limited CRL recharge instruction is preferably the maximum current instruction authorized by the battery, i.e. is equal to or less than the CR instruction. Alternatively, the CRL recharge instruction may be an instruction specifically controlling the stopping of the recharge, which may be independent of the CR instruction used to control the recharge of the battery. It does not necessarily express a maximum recharge current. In this case, the CRL instruction may be any instruction capable of command the end of recharge protocol. The CRL instruction commands the stopping of recharge before reaching the maximum SOC state of charge to avoid degradation of the cells, in particular separation of the electrodes and separators internal to the cells.

[0061] In another variant of the method, the recharging instruction is a target maximum SOC charge level conditioning the triggering of the stopping of the recharging. The method comprises the determination of a maximum SOC charge level authorized for recharging as a function of the value of the parameter P. During recharging, the computer of the battery system continuously monitors the state of charge of the battery and stops recharging when the maximum authorized SOC is reached.

[0062] For example, a table, recorded in the memory of the computer 2, includes values ​​of the maximum charge level of the battery associated with values ​​of parameter P, representative of the measured pressure or elongation. Depending on the measured value P, the table delivers the maximum authorized charge level.

[0063] In particular, when the parameter P is equal to or greater than the threshold SL, the maximum authorized SOC level is configured at a value lower than the maximum available SOC level. This maximum authorized level corresponds to the maximum acceptable pressure with regard to a risk of rupture of the frame or the cells. Thus, according to the method, when the state of charge reaches the maximum authorized level established according to the parameter P, the method controls the stopping of the recharging.

[0064] The advantage of this variant is that it also allows the user to be shown a virtual state of charge level, as a percentage, based on the permitted charging range instead of an available charging range. The charge level can thus be reported on a scale of [0%-100%] of the permitted range. This avoids any possible misunderstanding of the limitation function by the user, where the user would consider the early stopping of charging as a malfunction of the battery system.

[0065] In [Fig.3], a graph is presented illustrating the operation of the invention for controlling a recharge of the battery, in particular for controlling the stopping of the recharge when the internal pressure of a battery reaches the predetermined threshold SL.

[0066] On the abscissa axis, the evolution of the aging of the battery is represented as a function of the SOHc parameter, expressed in % by the ratio between the maximum quantity of energy storable at a given time and the maximum quantity of energy storable in the new state of the battery.

[0067] On the left ordinate axis, the value of the parameter P is represented, which is representative of the internal pressure. The measured pressure P is between 5k.N, in the situation at the beginning of the battery life, and 25k.N, in the usual situation at the end of the battery life. The threshold SL, illustrated by the double horizontal line, is established in this example at 25kN. The Psoc0% curve expresses the value of the pressure P measured for a current state of charge of the battery at SOC=0%. The Psocioo% curve expresses the value of the pressure P measured for a current state of charge of the battery at SOC=100%. The value of the pressure P measured by the strain gauge varies between these two curves according to the value of the current SOC throughout the life of the battery. This is the breathing phenomenon. In addition, we observe that the average value P increases as the battery ages.

[0068] On the right-hand ordinate axis, the value of the maximum state of charge of the battery that can be authorized in accordance with the method according to the invention is indicated. SOCmax is represented by a double-line curve and is between 0% and 100% and corresponds to the authorized range of use of the battery. The value of SOCmax at the start of life is equal to 100% and remains constant as long as the measured pressure is below the threshold SL. The value of SOCmax gradually decreases as a function of the pressure when the pressure P reaches the threshold SL.

[0069] There are two phases of battery life UT1 and UT2. UT1 corresponds to the life phase during which the measured pressure is lower than the threshold SL regardless of the value of the SOC. The method according to the invention does not impose a recharge limitation. UT2 corresponds to a phase where the aging SOHc is greater than 20% and corresponds to a life phase where the measured pressure Psocioo% can reach the value of the threshold SL depending on the value of the SOC.

[0070] For UT2, the control method according to the invention imposes a limitation of the recharging setpoint as soon as the pressure reaches the threshold SL. It can be seen that the value of the pressure P peaks at the value of the threshold SL. This is the consequence of the recharging limitation according to the method. In this phase, the maximum rechargeable state of charge value SOCmax becomes lower than the maximum SOC level of the battery, established at SOCmax=100%. The more the pressure increases, the more the SOCmax decreases because the stopping of recharging is controlled for lower states of charge in accordance with the invention. This makes it possible to extend the use of a battery in a controlled and optimal manner, in return for a reduction in the SOCmax during the UT2 period.

[0071] In dotted lines, the value of the pressure Psocl00% has been extended for a SOCmax of 100% and the value of SOCmax=100%, assuming that the recharge control method according to the invention would not be applied. It is observed that by maintaining the maximum authorized SOC at 100% during UT2, the pressure Psocl00% would exceed the threshold SL. This situation is subject to the risk of fire at the level of the cells or rupture of the cell frame. Generally, the use of the battery is terminated. The invention avoids this by controlling the end of the recharge in accordance with the method to maintain the pressure less than or equal to SL.

[0072] Several embodiments of the battery system are now described, differing in the arrangement of the pressure measuring means.

[0073] In [Fig.4a] and 4b, a first alternative embodiment of the module 3 of a battery system is described in which the measuring means 4 is a pressure sensor. According to a variant of the first embodiment, as illustrated in [Fig.4a], the sensor 4 is fixed between the frame 5 and an electrochemical cell 9. According to a second variant, as illustrated in [Fig.4b], the sensor 4 is fixed between two electrochemical cells 9.

[0074] In a second embodiment, in which the battery system is provided with several electrochemical cell modules, and in which each module comprises a rigid frame enclosing the group of cells, each module or only a selection of the modules comprises at least one means for measuring the parameter P. Each module or the selection of the modules can be equipped with a strain gauge and / or a pressure sensor.

[0075] In a third embodiment, of so-called “Cell to Pack” technology, the frame forming the pack is equipped with one or more strain gauges and / or one or more pressure sensors between the frame and a cell, and / or between two cells.

[0076] In a fourth embodiment, using so-called “Pouch Cell” technology, the pressure measuring means is fixed to the surface of the film, or between two cells.

[0077] Finally, the battery system may comprise a single electrochemical cell or comprise a plurality of cells.

Claims

Claims

1. Battery system (1) comprising elements (9) for storing electrical energy, a control means (2) capable of calculating a recharge instruction (CR, CRL) and a means (5) for clamping the elements (9), characterized in that it further comprises a means (4) for measuring a parameter (P) representative of a measured pressure which is exerted by the elements (9) on the surface of said means (5) for clamping and in that the control means (2) delivers a limited recharge instruction (CRL) as a function of said parameter (P).

2. System (1) according to claim 1, characterized in that the measuring means (4) comprises at least one strain gauge delivering a measurement of the elongation (M) of the means (5) for gripping.

3. System (1) according to claim 1 or 2, characterized in that the measuring means (4) comprises at least one first pressure sensor fixed between the elements (9) and the means (5) for clamping.

4. System (1) according to any one of claims 1 to 3, in which the elements (9) are electrochemical cells, characterized in that the measuring means (4) comprises at least one pressure sensor fixed between two electrochemical cells on the surface of one of said two cells.

5. System (1) according to any one of claims 1 to 4, characterized in that the means (5) for enclosing is a rigid frame made of metallic material.

6. An electrified vehicle comprising a battery system (1) according to any one of claims 1 to 5.

7. Method for controlling recharging for a battery system (1) according to any one of claims 1 to 5, characterized in that it comprises the following steps: - Determining a parameter (P) representative of a measured pressure which is exerted by the elements (9) for storing electrical energy on the surface of said means (5) for enclosing, - Controlling a first limited recharging instruction (CRL) as a function of said parameter (P).

8. Method according to claim 7, characterized in that the control of the first limited recharge instruction (CRL) consists of determining a limitation coefficient (CL) of the recharge as a function of the parameter (P) in relation to a limitation threshold of the recharge (SL), the value of the first limited recharge instruction (CRL) being a function of a second recharge instruction (CR) multiplied by the limitation coefficient (R).

9. Method according to claim 8, characterized in that, when the value of the parameter (P) is greater than or equal to the limitation threshold (SL), the limitation coefficient (CL) is equal to a first value controlling the stopping of the recharging of the battery system (1).

10. Method according to claim 8 or 9, characterized in that, when the value of the parameter (P) is lower than the limitation threshold (SL), the limitation coefficient (CL) is equal to a second value which is a function of a difference between the value of the parameter (P) and the limitation threshold (SL).

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